1. Field of the Invention
The present invention relates generally to agricultural seeders that produce open furrows in the soil into which seeds are placed, and more particularly, to an improved seed firming wheel and method of attaching and operating said firming wheel for use with such seeders in securing seed-to-soil contact.
2. Description of the Prior Art
Agricultural planting methods continue to evolve in response to widespread adoption of “no-till” or “reduced-till” crop production techniques with greatly reduced dependence on tillage of the soil, and in which the next crop's seeds are often placed directly into the previous crop's stubble or crop residues. No-till or reduced-till seeding differs greatly from seeding into a tilled seedbed. The soil conditions for no-till seeding are typically wetter than those dried by tillage, due to the mulching effect of the crop residue remaining on the soil surface. No-till soils are also typically more structurally stable than tilled soils, as the soil particles are “aggregated” or held together by old roots, fungi, and other organic substances and molecular attractions binding the particles together.
The value of pressing newly planted seeds into the soil has likely been known since the dawn of agriculture, and in-furrow firming wheels were clearly described and depicted at least as early as 1908 in Davis, U.S. Pat. No. 939,812. Some earlier “presser” wheels are taught by Patric et al., U.S. Pat. No. 404,108, issued in 1889, although these firming devices were relatively wide and further rearward than the device described in Davis '812. These early firming devices also essentially allowed (and relied upon) considerable loose soil to slough into the furrow ahead of the firming device, and are more in the vein of a modern ‘packer’ or ‘press’ wheel operating upon the soil surface and compressing all of the soil filled over the seed. Arnett, U.S. Pat. No. 345,403, issued in 1886, in describing a down-force system of dead weights for drill openers because “machines of this type, which are commonly operated on unplowed sod-land . . . ” [lines 18-19], also depicts press wheels “for the purpose of closing the furrow and covering the seed” [lines 47-48] which were apparently intended to also achieve seed firming to some extent. The different methods and actions of such wheels on freshly formed furrows and planted seeds becomes still more important in no-till conditions due to the greater structure or resilience of no-till soils as compared to tilled soils, which renders pressing from the soil surface ineffective and damaging to the seed environment. Soils which are eroded or which have otherwise suffered degradation from tillage, as well as soils that naturally have high clay content and/or low organic matter content, will be more susceptible to damage from excessive pressing above the seed, especially when those soils are damp.
In no-till seeding, the wetter and more structured soils generally prevent press wheels on the soil surface from performing the seed-firming and furrow-closing functions adequately. The sidewall of the furrow formed in no-till seeding does not crumble easily as does the sidewall in tilled conditions, where the soil had previously been loosened and fluffed by tillage. Accordingly, very high pressures are sometimes applied to the packing or closing wheels in an attempt to squeeze the furrow sidewalls back together. This typically results in poor seedling emergence because the soil in the furrow is more compressed at the surface compared to soil near the seed, sometimes to the extent of having a void immediately above the seed but with extremely compressed soil at the surface. In this instance, seed germination may fail due to the drying of air in the void, or the seedling may leaf underground in the void, or the seedling will encounter great difficulty pushing itself through the dense layer of soil, which will slow and weaken the seedling or even kill it.
Some improvements have been made by separating the seed firming and furrow closing functions. This is typically only possible where the depth-gauging function is already accomplished independently of the packing or closing wheel, as in the configuration where depth-gauging wheels travel alongside the furrow opening discs. Seeds are firmed into the soil in the bottom of the furrow by a narrow rolling wheel or sliding-type firmer exerting a relatively small amount of pressure onto the seed after it has been placed by the furrow openers and seed-directing tube.
The lineage of rolling in-furrow firming wheels extends down through the years, including firming wheels affixed to the opener subframe so as not to move during field operation (as taught by Lemmon, U.S. Pat. No. 2,577,775, and Jennings et al., U.S. Pat. No. 4,307,674), firming wheels suspended from a closing frame, and firming wheels such as Davis '812 wherein the wheel and trailing attaching arm is free to pivot vertically and urged downward by a spring tensioning device (such as further taught by Yoder et al., U.S. Pat. Nos. 5,826,524 and 5,724, 903; and by Johnson et al., U.S. Pat. Nos. 5,398,625, 5,494,339, and 5,676,429). Some of the small-diameter (e.g., 5-inch diameter) firming wheels, such as envisioned by Yoder and Johnson, did in reality encounter numerous difficulties in field operation including mud and stubble accumulation near the wheel's axis of rotation and including the juncture with the attaching arm. Other difficulties have ensued with the attaching arm and spring apparatus being located between (on “double-disc” designs) the furrow-opening blades and gauge wheels, which contributes to mud and straw accumulation, as well as making awkward the adjustment and service of the attaching arm and spring. Most of the planter models sold in North America in the last 30 years have subframes that extend rearward of the opener blades and gauge wheels, preventing the simple installation of large-diameter firming wheels in close proximity to the blades.
As compared to small firming wheels, the large-diameter (9-or 10-inch) firming wheels of appropriately narrow construction have encountered considerably more success, such as what is taught by Bigbee (U.S. Pat. No. 4,760,806) and improved by Prairie et al. (U.S. Pat. No. 6,386,127), embodied in the firming wheels of the John Deere 50, 60, and 90-series models of single-disc opener grain drills and in the Case-New Holland SDX series of drills, respectively. These prior art designs utilize a firming wheel mounting that enables the wheel and attaching arm to pivot vertically from the upper or forward end of the attaching arm, such that the wheel is able to move independently of the opener. In this way, the wheel and arm are trailing from the radial pivot point. Trailing arms generally require substantial pressure to ensure sufficient firming action by the firming wheel, and often are further rearward than desired, due to the necessities of clearance for the arc of travel of the firming wheel during field operation.
Virtually none of the planter models currently marketed in North America employ large-diameter in-furrow firming wheels (or any in-furrow firming device at all), apparently because packing the soil from the surface downward is perceived as adequate by the currently dominant tilled-seedbed market. However, small-diameter (approximately 5-inch) “seed-lock” firming wheels, and the attaching mechanisms from which the wheel trails, have at various times been sold in the North American markets by both OEM planter manufacturers (Kinze, J D, Great Plains, AGCO White) as well as aftermarket suppliers (Yetter, J S Ag Innovations). These small-diameter wheels were quite popular for a few years in the mid-1990s, until the realization that plugging with mud and crop residues was a serious problem.
Sliding seed-firming devices also have a long history, appearing (but not described) in 1889 in Patric et al. '108, although as previously discussed, the device was neither shaped nor positioned to function in the furrow proper, but rather the device would likely operate in the vestiges of the furrow and on top of considerable loose “fill” soil that had sloughed back into the furrow after the opener blades had passed, and the relatively wide Patric firming device itself would likely tend to drag still more soil into the furrow with its forward end as it slid. The “presser-foot” is further depicted in Patric et al., U.S. Pat. No. 410,438, and in Packham, U.S. Pat. No. 530,962. More recent inventions have been true in-furrow sliding firming devices, such as described in Keeton, U.S. Pat. Nos. 5,425,318 and 5,673,638, as well as Peterson et al., U.S. Pat. No. 6,119,608. Many of these sliding firming devices are hindered in their performance by mud or damp soil accumulation on the lower edges, especially if some soil disturbance occurs ahead of the firming device so that it no longer is operating in a ‘clean’ cut, or if insufficient pressure is applied to the sliding firming device. Soil accumulation on the underside of the firming device can result in dragging of seeds, and in a poor firming action. Sliding firming devices may also exhibit rapid wear in many soil conditions, unless made from exotic materials.